1. Field of the Invention
The present invention relates to an inkjet printer, and more particularly, to a paper feeding device for an inkjet printer.
2. Description of the Related Art
An inkjet printer is a printing apparatus that creates an image on a sheet of paper by spraying ink through a print head, and typically has a front insert front out (FIFO) feeding structure in which paper is supplied and discharged in the same direction.
FIG. 1 shows an example of an inkjet printer having the FIFO feeding structure. Referring to FIG. 1, the inkjet printer comprises a print head 10 that sprays ink onto a sheet of paper, a feed cassette 20 in which paper is stacked, and a paper feeding device 30 that supplies the stacked paper to the print head 10. The paper feeding device 30 comprises a pickup roller 31 that picks up the stacked paper, a drive roller 32 that conveys the picked up paper, and a feeding roller that conveys the conveyed paper towards the print head 10 in increments.
When the pickup roller 31 is driven, the paper stacked in the feed cassette 20 is separated sheet by sheet by a separation wall 21 and picked up. The picked up paper proceeds between the drive roller 32 and a pinch roller 34 pressing the drive roller 32 with a predetermined force, and is moved towards the feeding roller 33 by the drive roller 32. The paper conveyed to the feeding roller 33 is transferred to below the print head 10 by the feeding roller 33 and the friction roller 35 disposed above the feeding roller 33. When the paper arrives on the paper guide 40 disposed below the print head 10, the print head 10 prints an image by spraying ink onto the paper while moving left and right along the guide bar 11. The discharge roller 50 discharges the paper with the image printed thereon outside the device.
Since it takes time for the print head 10 to spray ink on the paper while moving along a line, the feeding roller 33 line-feeds paper to the paper guide 40 at a predetermined interval. In order to line-feed, a line-feed (LF) motor (not shown) is used for driving the feeding roller 33. The LF motor not only drives the feeding roller 33 but also the pickup roller 31 selectively. That is, when the LF motor rotates forward, the feeding roller 33 is driven in the paper convey direction A. When the LF motor rotates backward, the feeding roller 33 rotates in the reverse direction B. Concurrently, a driving force is transmitted to the pickup roller 31 whereby the pickup roller 31 rotates in the paper pickup direction C and picks up the paper. Here, a swing gear or a one-way clutch selectively transmits a driving force to the pickup roller 31. When the paper picked up by the pickup roller 31 reaches the feeding roller 33 rotating in the reverse direction B by the drive roller 32, the LF motor rotates forward again thereby rotating the feeding roller 33 in the paper convey direction A. At this time, the pickup roller 31 rests on the paper as it does not receive any driving force, and the paper is line fed to the paper guide 40 by the feeding roller 33.
However, such a conventional paper feeding device 30 of an inkjet printer prevents the drive roller 32 and the feeding roller 33 from smoothly conveying the paper since the pickup roller 31 rests on the paper even after a sheet of paper is picked up. Accordingly, paper is not smoothly conveyed to the printer head. Thus, print quality deteriorates. Moreover, if the pickup roller 31 does not press the paper with the same load each time paper is picked up, the paper can be skewed or jammed.